1. Field of the Invention
The invention relates to a method of investigating the gait of a living being, more particularly a horse, by measuring the force exerted by its feet on the ground and of the location, duration and course in time of the application of force in the zone of a substantially horizontal measuring surface taking the form of part of the ground, the measuring surface being subdivided substantially at right angles to the direction of movement of the living being into elongate measuring sections parallel to each other and adjacent in succession in lamellar fashion. The invention also relates to a corresponding apparatus, wherein a force sensing device having a substantially rectangular force sensing surface and a plurality of measured value delivering sensors connected to an electronic evaluating unit are associated with each measuring section.
The process and apparatus produces results which are mainly usable outside medicine as intermediate results for assessing the gait of the particular living being, even if they may be used when making a diagnosis, too.
More particularly in the case of highly valuable horses such as racehorses, it is found to be necessary to obtain the fact that such measured values give notice of abnormalities and can often throw light on their causes, such measured values provide information concerning the present condition (fitness) of the horse and its racing chances at the moment.
2. Discussion of the Prior Art
Since every horse has its own individual gait, the gait can be measured and stored with the animal perfectly healthy and giving its best performance. The gait is then available as a basic pattern for a subsequent comparison with fresh measurements. Regular gait analyses enable deviations from the basic pattern of the gait to be detected earlier on, more particularly before the horse shows lameness. As a result, for example, a horse in poor condition can be gently treated, or if necessary measures can be taken in good time to prevent the progress of a disease.
U.S. Pat. No. 4,233,845 states that the potential performance of a horse depends on the time during which two or more hoofs are simultaneously in contact with the ground during one step. The performance potential also depends on the time during which all four legs are simultaneously not in contact with the ground during one step. For these reasons U.S. Pat. No. 4,233,845 proposes that the horse should be put into a high speed gait and the time of contact determined during which contact with the ground is made and then discontinued during successive steps at this gait. The overlapping time during this step is also measured, and also the speed of the gait. Conclusions concerning performance potential are drawn from these results. To determine the contact with the ground and the corresponding contact times, use is made of a high speed camera or the sound of the steps is recorded on a tape recorder placed on the horse or on the ground, while the speed is measured based on running distance and clock measurements. These recording procedures are much too expensive, and moreover the results attainable are much too imprecise to enable the gait at the moment to be compared with a stored previous gait--i.e. to detect deviations from the basic pattern in good time.
U.S. Pat. No. 4,195,643 discloses a method of determining the relation between a limit of pain and the physiological compressive force to be ascribed to the pain. The physiological compressive forces are recorded by a pressure plate system to produce an analog output signal with a direct voltage and an alternating voltage component. In a suitable analyzer, the direct voltage component and the alternating voltage component are then separated, whereafter an output signal derived from the alternating voltage component is generated which quantifies the pain limit. However, the coming lameness of a horse cannot be diagnosed before a pain limit is reached, and this method is unsuitable for the early detection of deviations from the basic gait pattern.
WO-87/01574 and U.S. Pat. No. 4,267,728 disclose how to investigate the gait of a human being by measuring the force exerted on a measuring area by means of force sensing devices disposed parallel to each other and adjacent in succession and connected to an electronic evaluating unit. Not only the force exerted, but also the locations where the force is exerted and the position of such locations in relation to one another are also determined. The result is supposed to yield information concerning the geometry of the footprints as a function of time and the relative arrangement of the footprints and the strength of pressure. However, the duration corresponding to the successive steps and the corresponding sequence of the application of force in time are not determined with a resolution which would be suitable for the early detection of deviations from the basic gait pattern, since this is quite unnecessary in the intended use of these prior art systems, which are basically intended for investigating the biomechanics of the human gait with reference to diagnosis and therapeutic measures. Moreover, in the system disclosed in WO-87/01574 the person to be investigated walks on a soft mat, and in the system disclosed in U.S. Pat. No. 4,267,728 on transparent beams arranged successively in parallel, which arrangement cannot be used or extrapolated for a horse, since if a horse senses or sees a change in the structure of the ground it immediately alters its gait in reaction thereto.
The Paper by S. Hirokawa and K. Matsumara entitled "Gait analysis using a measuring walkway for temporal and distance factors" published in Medical & Biological Engineering & Computing 25 (September 1987), pages 577-582, discloses a system for investigating the human gait which is similar to the system disclosed in WO-87/01574 and has the same disadvantages, so that it also is unsuitable for the early detection of deviations from the basic gait pattern, more particularly of a horse.
It is also known from U.S. Pat. No. 4,195,643 to investigate the gait of a living being (human being or horse) also by measuring the force exerted on a measuring surface by means of force sensing devices disposed parallel to each other and adjacent in succession and connected to an electronic evaluating unit. This system also determines not only the force exerted, but the locations of the exertion of force and the position of the locations in relation to one another. The result is supposed to yield information concerning the relative arrangement of the footprints of the human being or horse, and also the strength of the pressure as a function of time. However, in this system also the duration corresponding to the successive steps and the corresponding cause of the application of force in time is not determined with a resolution which would be suitable for the early detection of deviations from the basic gait pattern, since this is quite unnecessary in the intended use of the system, which is mainly aimed at investigating the biomechanics of the gait with reference to diagnosis and therapeutic measures. Moreover, the structure and dimensions of the measuring area provided cannot be used or extrapolated for investigating the gait of a horse; on the one hand the measuring area extends above the ground, which arrangement cannot be used for a horse, since the horse would immediately alter its gait in reaction thereto, and on the other hand the measuring surface with its dimensions of about 60.times.60 cm (whether subdivided or not) is unsuitably dimensioned and proportioned for the early recognition of deviations from the basic pattern of the sporting gait (running in human beings, trotting or galloping in horses), since this requires a substantially wider and longer measuring area.
CH-658726 and CH-669256 propose hydraulic pressure sensing devices for the measurement of the force exerted on a measuring surface by means of force sensing devices disposed parallel to each other and adjacent in succession and connected to an electronic evaluating unit. An incompressible liquid is disposed in a resilient tubular casing which can be acted upon by an external pressure, the casing being connected to a manometer or transducer. The wall of the tubular casing which receives the pressure is connected via the liquid to a pressure-transmitting longitudinal reinforcement. These devices merely determine the strength of a pressure. It is true that this may throw some light on the gait of a horse, but it is not adequate for the assessment of the gait.
U.S. Pat. No. 3,906,931 suggests electromechanical pressure sensing devices for the measurement of the force exerted on the measured area and of the locations where the force is exerted and the position of the locations in relation to one another. A number of strain gauges are disposed in four resilient rings acted upon by an external pressure. This apparatus actually allows instantaneously or as a function of time the determination of not only the total force exerted, but also of the locations where the force is exerted and the position of the locations in relation to one another, but the apparatus is intended solely to investigate the stance of a human being: it is unsuitable for investigating the gait of a human being, let alone for investigating the gait of a horse.
Apparatuses of a similar kind and having the same disadvantages are also known, for example, from U.S. Pat. No. 3,340,726 and U.S. Pat. No. 3,090,226.
Magnetic path sensors which can be used for the measurement of force are mentioned in general and briefly described in the "Manual of the electric measurement of mechanical values" by C. Rohrbach, published by VDI (Dusseldorf, 1967).